This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The current study is intended as a pilot study to generate data that examines the impact of oxytocin administration in individuals with Borderline Personality Disorder (BPD). BPD is a DSM-IV personality disorder characterized by chronic and pervasive symptoms of impulsivity, anger, affective instability and identity confusion. We hope to explore whether there is preliminary evidence of oxytocin modulation of social and stress related disturbances in BPD. If preliminary data are promising, the investigators plan to pursue a larger study. The current study will begin with recruitment of twenty adults with BPD and twenty normal control adults. After signing informed consent, subjects will undergo a psychiatric evaluation by a study psychiatrist who will determine preliminary diagnoses and eligibility, which will be determined by administration of the Structured Clinical Interview for DSM-IV Axis I Disorders and the Structured Interview for DSM-IV Personality Disorders SIDP-IV. A series of interviews will also be conducted to assess measures including past trauma, relationship styles, stress levels, trust, self-esteem and impulsivity among other measures. After the Baseline Evaluation, subjects will be scheduled to arrive at the clinical research center and will receive routine laboratory tests. Subjects will be randomized in a double-blind fashion to receive either oxytocin or placebo on their first challenge. The second challenge will be scheduled within 1 to 2 weeks after the first one, and each subject will receive the alternate condition. Challenge tasks will include the Profile of Mood States, the Lexical Decision Task, The Prisoner's Dilemma Game Task and the Trier Social Stress Test. Results of the challenge tasks and laboratory samples will be analyzed and compared. Hypothesis: It is hypothesized that oxytocin will cause enhanced trust-based prosocial cognitions and behaviors and diminished cortisol reactivity to psychosocial stress in both the healthy controls and the BPD group. It is expected that the BPD group will show greater benefits in trust-based prosocial cognitions and behaviors than the healthy controls under the oxytocin challenge. Conversely, we predict to see greater impairment in prosocial cognitions and behaviors in the BPD group than in the healthy controls under the placebo challenge.